The Pearl River Delta (PRD) region is an important area for air quality research. This study provides a year-long observation of aerosol species using aerosol mass spectrometry. The paper’s focus is given to secondary organic aerosols which account for about a quarter of submicron particle mass concentration. In general, the paper is well organized and clearly written. Presenting such an extensive observational dataset itself serves as a contribution to the atmospheric chemistry community. I only have a few minor comments on the current paper.

1. On the Q-ACSM data analysis: Previous studies used to have different categories for SOAs. For example, some studies have separated an aq-SOA (aqueous-processing SOA) component. Can the authors provide more information on the assumption and reasons for their choice of SOA categories?
2. Fig.3 & Fig.5: Earlies studies reported fast formation of sulfate at haze episodes, which seems to be different from the measurements shown here. Can the authors show the reasons?
3. The variations of boundary layer height may affect the interpretation of the formation mechanisms of aerosol species. Can the authors provide more quantitative results on its influence?

This study reported a year-long AMS measurement data for NR-PM1 in Guangzhou urban area of the PRD, China, and then discussed the possible formation pathways of SOA and its significant role on haze occurrences in the region. Indeed, long-term AMS data was relatively scarce and thus valuable for better understanding the source contribution and formation pathways of aerosols in the atmosphere. This paper also presented some interesting scientific findings, e.g., haze formation mechanisms differed much among distinct seasons, significant roles of the coordination of gas-phase photochemistry and subsequent aqueous-phase reactions in quick daytime SOA formations, etc. However, in my opinion, several parts of the manuscript were not well organized and clearly described. Detailed comments were listed below.

1. L46-47, “reaching about 1.7 times that of primary organic aerosols …”, grammar error.
2. Introduction: should be entirely revised. Although long-term AMS data is valuable, it is not a scientific goal. The authors should more focus on the present understanding and deficiency of SOA formation, and how the long-term AMS data can help understanding it. The authors also need to summarize the main conclusions of previous long-term AMS studies, not just list these references, and clarify the advantage of this study.
3. L123, “from which black carbon (BC) mass concentrations in winter and early spring”, this sentence is confusing.
4. Q-ACSM data analysis: this section was too redundant, I suggest to move some detailed analysis to supplement.
5. 3.1: L229, L234, etc. In this section, the PBL and rainy conditions were repeatedly referred to explain the seasonal variations of PM1 and chemical componets. Could you provide detailed data about PBL and precipitation for it?
6. L249-250: grammar error.
7. L259-261, why are there more traffic emissions in winter? Please provide more evidences.
8. L265-267, this sentence is confusing, please clarify it.
9. 3.2 Significant contributions of secondary organic aerosols to haze formations in all seasons: it seems that the authors try to highlight the role of SOA in haze formations, however, I think it is overstated, at least in the section title. For example, in L286-299, the contribution of OA in generally decreased when PM1 concentration increased in fall. Similar trend of SOA could be found in other seasons (Figure 5).
10. L431, 436, NO+ and NO2+ were not in right format.